1. Technical Field
The present invention relates to a detent escapement and to a timepiece into which the detent escapement is incorporated. Particularly, the present invention relates to a detent escapement which is configured so as to decrease escapement error and to a mechanical timepiece into which a detent escapement configured as above is incorporated.
2. Background Art
In the related art, a “detent escapement” (chronometer escapement) has been known as one type of an escapement of a mechanical timepiece. As a representative mechanism form of the detent escapement, conventionally, a spring detent escapement and a pivoted detent escapement have been widely known (for example, refer to NPL 1 below).
Referring to FIG. 20, the conventional spring detent escapement 800 includes an escape wheel and pinion 810, a balance 820, a detent lever 840, and a balance spring 830 which is configured by a plate spring. An impulse pin 812 is fixed to a large collar of the balance 820. A locking jewel 832 is fixed to the detent lever 840. An unlocking jewel 824 is fixed to the large collar 816. The impulse pin 812 and the unlocking jewel 824 are configured so as to be able to contact a tooth portion 112 of the escape wheel and pinion 110.
Referring to FIG. 21, the conventional pivoted detent escapement 900 includes an escape wheel and pinion 910, a balance 920, a detent lever 930, and a balance spring 940 which is configured by a spiral spring (swirling spring). An impulse pin 912 is fixed to a large collar of the balance 920. A locking jewel 932 is fixed to the detent lever 930. An unlocking jewel 924 is fixed to the large collar 916.
Unlike a crab toothed lever escapement which is widely used currently, as a characteristic common to the escapements of the types shown in FIGS. 20 and 21, since power is directly transmitted from the escape wheel and pinion to the balance, there is an advantage in that loss of power (transmission torque) in the escapement can be decreased.
In addition, the conventional detent escapement includes an escape wheel and pinion (1), a balance, a detent (11) which supports a stop pawl (21), and a restricting plate (5) which is fixed to the balance. The detent escapement includes a balance spring (12), the inner end of which is integrated into the detent (11) (for example, refer to PTL 1 below).